Field of the Invention
Preferred embodiment relates to the art of a selectable one-way clutch adapted to selectively enable a torque transmission only in one direction and a torque transmission in both directions.
Discussion of the Related Art
PCT international publication WO2013/040135 describes an example of a selectable one-way clutch (to be abbreviated as “SOWC” hereinafter). In the selectable one-way clutch taught by WO2013/040135, a control plate is disposed between a rotatable pocket plate and a notch plate, and pawls is adapted to be projected to the notch plate side when apertures formed through the control plate is situated on corresponding site of the pawl held in the pocket plate. A leading end of each pawl is individually fitted into engagement with notches formed on the notch plate to bring the pocket plate into engagement with the notch plate. Consequently, a torque transmission between the pocket plate and the notch plate is enabled by rotating the notch plate relatively with the pocket plate. When the notch plate is rotated in the opposite direction, the pawl is pushed toward the pocket plate by the edge of the notch so that the pocket plate is brought into disengagement from the notch plate to disable the torque transmission therebetween. Consequently, the SOWC is brought into an over running state. The pawl is pushed into the pocket by further displacing the aperture from the pocket and so that the pawl is completely brought into disengagement from the notch. Consequently, the pocket plate and the notch plate are allowed to rotate relatively to each other in both directions.
That is, the control plate of the SOWC taught by WO2013/040135 is rotated by a relatively small actuator or spring to selectively push the struts into the pockets. Each clearance between those plates is rather narrow and hence lubricant is applied to the clearance to reduce friction. If the notch plate is rotated relatively with the pocket plate in the ratchet direction (opposite to the over running direction) in the SOWC in the overrunning state, the control plate may be rotated unwillingly by a drag torque resulting from such rotation to bring the strut into engagement with the notch. Especially, if a temperature of the lubricant is low and hence viscosity thereof is high, such drag torque to bring the strut into engagement unwillingly is increased.
Aspects of preferred embodiment has been conceived noting the foregoing technical problems, and it is therefore an object of the preferred embodiment is to provide a selectable one-way clutch which can prevent an unintentional engagement thereof.